This invention relates to vulcanized elastomers containing urethane groups produced by the casting process, and to a process for producing the same.
It has already been disclosed in German Auslegeschrift No. 2,602,495 (U.S. Pat. No. 4,104,265), that elastomeric molded products can be produced from liquid diene polymers which contain functional groups, reinforcing fillers, chain lengthening agents (such as isocyanates or amines) and vulcanizing agents, optionally in the presence of polyethers or polyesters, by vulcanizing the mixture of the abovementioned components, first at temperatures from 20.degree. to 125.degree. C. and then, in a second stage, at temperatures above 140.degree. C.
The liquid diene polymers used in this process must have a degree of functionality of from 1.8 to 2.0. The use of diene polymers having such a degree of functionality is a disadvantage because these polymers are generally difficult to obtain since they are usually prepared by a relatively complicated anionic polymerization.
Moreover, the elastomers obtained according to the above-mentioned German Auslegeschrift still have so little structural stability after chain lengthening that vulcanization must be carried out in the same mold.
Another disadvantage of the known process is that the components must be mixed together by means of rollers as in the case of rubbers, which entails a high consumption of energy.